Integrated Microsystems: Device and Technology Challenges

Integrated sensors have become increasingly important over the last few years in efforts to extend microelectronic-based signal processing and control into a broad range of new areas, including industrial automation, automotive systems, biomedicine, and environmental monitoring. Such devices are evolving from simple silicon transducers into sophisticated integrated microsystems containing sensors, actuators, and signal-processing electronics, all integrated on a common substrate. Highly integrated modules containing these devices together with embedded microprocessors and wireless communication links are now emerging to form ''smart'' microinstrumentation systems capable of distributed information gathering and closed-loop control. This paper discusses the device and technology options available for integrated sensors along with the challenges in integrating them with micropower electronics to form microsystems. Technology, materials, microstructures, process integration, interface circuits, CAD, and packaging are all areas where additional progress is needed, each of which offers the device designer important challenges. High-aspect-ratio dry etching, low-temperature wafer bonding, characterization of materials to 16b and beyond, precision readout and compensation techniques, better and more integrable actuation mechanisms, and chip-level encapsulation are but a few specific topics for further research. As examples of emerging microsystems, integrated microelectrode arrays are now capable of interfacing with biological neural networks at the cellular level using microstructures ≪30μm wide and containing recording electrodes, stimulating electrodes, thermal sensors, and chemical delivery channels. Three-dimensional arrays of such devices promise the ability to monitor/control most neural activity within selected volumes of tissue within the coming decade.